Effects of temperature parameters on thermal-optical analysis of organic and elemental carbon in aerosol

Author： Zhi Guorui Chen Yingjun Sheng Guoying Fu Jiamo

ISSN： 0167-6369

Source： Environmental Monitoring and Assessment, Vol.154, Iss.1-4, 2009-07, pp. : 253-261

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Abstract

Thermal–optical analysis (TOA) is a popular method to determine aerosol elemental carbon (EC) and organic carbon (OC) collected on quartz fiber filter. However, temperature protocol adopted in TOA has great effects on OC and EC results. The purpose of this study is to investigate and quantify the effects of maximum temperature (T_max) and residence time (RT) for each step in helium stage on ECOC measurements. Fourteen typical source samples and 20 ambient samples were collected and six temperature programs were designed for this study. It was found that EC value decreases regularly as T_max ascends, i.e., EC results from T_max of 650°C, 750°C and 850°C are 0.89 ± 0.06, 0.76 ± 0.10, 0.62 ± 0.13 times EC value from T_max of 550°C, respectively, and the magnitude of EC drop (EC_d, percent) is significantly correlated with OC abundance in total carbon (R_OC/TC), expressed as EC_d = 66.8R_OC/TC − 14.4 (r = 0.87); pyrolized OC (POC) values are also sensitive to T_max, but there are various trends for samples with different OC constituents. On average of the samples studied here, prolonged RT reduces EC values by only 3%, almost negligible compared to the effect of T_max, and reduces POC by 9%, much less than that by previous report.